Desertification: Natural Background and Human Mismanagement

320 Pages·1991·9.595 MB·English

by  Professor Dr. Monique Mainguet (auth.)

Springer Series 9
in Physical Environment
Managing Editor
D. Barsch, Heidelberg
Editors
I. Douglas, Manchester . F. Joly, Paris
M. Marcus, Tempe· B. Messerli, Bern
Advisory Board
v.
F. Ahnert, Aachen . R. Baker, Thcson . R. G. Barry, Boulder
H. Bremer, K~ln . D. Brunsden, London . R. U. Cooke, London
R. Coque, Paris . Y. Dewolf, Paris . P. Fogelberg, Helsinki
O. Frttnzle, Kiel . I. Gams, Ljubljana . A. Godard, Meudon
A. Guilcher, Brest . H. Hagedorn, Wilrzburg . 1. Ives, Boulder
S. Kozarski, Poznan . H. Leser, Basel . 1. R. Mather, Newark
1. Nicod, Aix-en-Provence . A. R. Orme, Los Angeles
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A. Semmel, Frankfurt/Main . G. SUlblein, Bremen
H. Svensson, Kebenhavn . M. M. Sweeting, Oxford
R. W. Young, Wollongong
Volumes already published
Vol. 1: Earth Surface Systems
R. Huggett
Vol. 2: Karst Hydrology
O. Bonacci
Vol. 3: Fluvial Processes in Dryland Rivers
W.L. Graf
Vol. 4: Processes in Karst Systems
Physics, Chemistry and Geology
W. Dreybrodt
Vol. 5: Loess in China
T. Liu
Vol. 6: System-Theoretical Modelling in Surface Water Hydrology
A. Lattermann
Vol. 7: River Morphology
1. Mangelsdorf, K. Scheurmann and F. H. WeiB
Vol. 8: Ice Composition and Glacier Dynamics
R. A. Souchez and R. D. Lorrain
Vol. 9: Desertification
Natural Background and Human Mismanagement
M. Mainguet
Volumes in preparation
Vol. 10: Fertility of Soils
A Future for Farming in the West African Savannah
C. Pieri
Vol. 11: Sandstone Landforms
R. Young and A. Young
Vol. 12: Numerical Simulation of Canopy Flows
G. GroB
Monique Mainguet
Desertification
Natural Background
and Human Mismanagement
With 84 Figures
Springer-Verlag
Berlin Heidelberg New York London
Paris Tokyo Hong Kong Barcelona
Budapest
Professor Dr. MONIQUE MAINGUET
Universite de Reims
Laboratoire de Geographie Physique Zonale
57, Rue Pierre Thittinger
51100 Reims, France
Cover picture:
Djida, Vallee du serpent. Red dune system, interspersed with trees, very degraded after
the drought t 968 -1985. This photograph was taken in July 1985, just after the first
rain. The trees, appearing almost lifeless, show some foliage among dry branches. The
soil apposes a red, almost reactivated dune (background), and an interdunal depression
with little, discontinuous and broken crusting (foreground).
(Copyright by M. Mainguet)
ISSN 0937-3047
ISBN-13: 978-3-642-97255-3 e-ISBN-13: 978-3-642-97253-9
001: 10.1007/978-3-642-97253-9
Library of Congress Cataloging-in-Publication Data. Mainguet, Monique, 1937 - Desertification:
natural background and human mismanagement / Monique Mainguet. p. cm. - (Springer series
in physical environment; 9) Includes bibliographical references and index.
1. Desertification. I. Title. II. Series. GB611.M24
1991 551.4'15 - dc20 91-14151
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3213145-543210 - Printed on acid-free paper
"Development is a gradual process of learning:' (Eicher 1986)
"The relationship between people and nature in most of Africa has been ex
tractive: people took crops, and wood, and put nothing back, but gave nature
time and space to restore herself. That relationship depended on an abun
dance of land and forests. But as population density grew, that abundance
could no longer be taken for granted. Nature is no longer given time to restore
herself. Her capital of resources is being depleted, and the whole system
grinds gradually downhill:' (Harrison 1987)
"I see a fulfilment of the great Law of all worlds, that while the wisdom of
Man thinks it is working one thing, the wisdom of Nature constrains it to
work another, and quite a different and far better thing:' (Abbott 1884)
Preface
The different phenomena called desertification have attracted most
attention in those countries where their impact on human life is most
severe. Great human misery, malnutrition, starvation, and the under
mining of the ability of these drylands to support life have most often
been described in the Sahel of Africa and in western Rajastan (India).
Are they in fact caused by one or several aspects of what is called
desertification?
When I agreed to write this book on Desertification: Natural
Background and Human Mismanagement, I was well aware that there
is an extensive and growing body of literature on the subject. The only
printout of desertification bibliography of the Office of Arid Land
Studies, University of Arizona, at the beginning of the 1980's was
almost 30 m long! So why another book? Was it because I felt:
1. It was necessary to offer further shades of meaning to the concept
of desertification. Is desertification an existing phenomenon? In
which ecosystem does land degradation reach the level of deser
tification?
2. How much land degradation is due to natural causes and how
much to man's activities?
3. At what level can the solutions to land degradation be applied? Do
seeds of hope exist?
I also agreed to write this book because I think that my fieldwork
in the last three decades in the severely drought-prone countries of
Africa and in almost all the deserts of our planet has provided me
with valuable first-hand experience and information.
I use the world "experience" as it is defined by Claude Bernard:
"Dans la langue fran~aise Ie mot experience au singulier signifie ...
l'instruction acquise par l'usage de la vie".
The concept of desertification is relative in connection with
human activities. Without people there is no desertification.
1. People are the producers of desertification. Why has there been the
temptation to maximize the natural causes and to minimize the
human responsibilities?
2. Desertification is mainly a function of mistaken human optimism
about rainfall; it can be due to the assumption that good rains will
VIII Preface
always fall. However, in a year of poor rains, agricultural methods
suitable only for years of good rains can lead to crop failure, lack
of adequate cover, wind erosion, and desertification.
3. Desertification can be considered as a useful alarm signal from the
environment to indicate when human activities have reached the
threshold of tolerance.
This book is not an attempt to synthetize all the available scien
tific information on desertification, but a selection of confirmed in
formation highlighting the problem.
I shall also try to identify those policies which could prevent
desertification and those which can improve land degradation which
has not reached the point of being irreversible.
MONIQUE MAINGUET
Acknowledgements
When I decided to write this book in English, I knew that I was taking
on a mountainous task. It might well have become too frustrating
without the help I have had from many sources too numerous to men
tion individually. I must, however, express my gratitude to four people
in particular.
Mrs. Mary Peel agreed to read through the first draft and amend
any mistakes in my English. In the outcome, this resulted in much
more than that. Because of her familiarity with much of the basic ma
terial acquired over 40 years from her late husband Ronald Peel,
himself an arid lands specialist, she was able to correct and question
my meaning in a way which made me clarify my thinking and the aim
and development of my arguments on numerous points.
Professor W. Richards of the University of Maiduguri also agreed
to read the book and to offer his criticisms and advice on the plan
and content. He made me aware that I had run away from dealing
adequately with all the complexities of the African drylands.
My assistant, Marie-Christine Chemin, responded unfailingly to
my demands on her for the organizing of the material at the final
stages.
Finally, my debt to my husband Serge is immeasurable.
MONIQUE MAINGUET
Contents
1. What is Desertification?: Definitions and Evolution
of the Concept ................................ .
1.1 Definitions of Desertification .................... . 1
1.2 The Evolution of the Concept of Desertification ... . 6
1.2.1 The Age of Awareness .......................... . 6
1.2.2 The Age of Wrong Perception or Misconception ... . 8
1.2.3 The Age of Doubt ............................. . 9
1.2.4 The Myth of the Encroaching Desert ............. . 12
1.2.5 The Dawning of the New Realism ............... . 15
1.3 General Conclusion, Chapter 1 .................. . 16
2. "Desertification" or Land Degradation:
Location and Dimension in Time, Vulnerability
of Soil and Plants in Drylands .................. . 17
2.1 Introduction .................................. . 17
2.2 Location of "Desertification" or Land Degradation,
Threatened Areas and Drought-Prone Regions ..... . 17
2.3 Dryness Ratio and Drought ..................... . 21
2.3.1 Dryness Ratio ................................. . 21
2.3.2 Drought ...................................... . 23
2.3.2.1 Meteorological Drought ....................... .. 24
2.3.2.2 Hydrological Drought .......................... . 25
2.3.2.3 Agricultural Drought ........................... . 32
2.4 The Droughts of the 1Wentieth Century Throughout
the World ..................................... . 34
2.5 The Vulnerability of Soils in Drylands ............ . 36
2.6 The Survival of Plants in Dry or Seasonally Dry
Ecozones ...................................... 39
2.7 General Conclusion, Chapter 2 ................... 41
XII Contents
3. Dimensions in Space of "Desertification" or Land
Degradation: The Degree and Specificity in Each
Continent ...................................... 42
3.1 Introduction: Global Dimension in Space
of "Desertification" ............................. 42
3.2 Sub-Saharan Africa: lhlditional Extensive
Agriculture, Unadapted High Technology.
and Land Degradation .......................... 43
3.2.1 Droughts in the Sahel ........................... 44
3.2.1.1 Paleo-Droughts and Historical Droughts ........... 44
3.2.1.2 20th Century Droughts .......................... 45
3.2.1.3 Drought and Shifting Isohyets in Eastern Mali.
Where Are the Most Severe Effects of Drought? .... 47
3.2.2 The Bioclimatological Ecozones .................. 54
3.2.3 Traditional Land Occupation. Potentialities and
Agricultural Limits in High Climatic Risk Drylands. 56
3.2.3.1 Hunting ....................................... 57
3.2.3.2 Fishing ........................................ 57
3.2.3.3 Domesticated Stock-Keeping ............. , . . . . .. . . 58
3.2.3.4 Agriculture in Sub-Saharan Drylands .............. 59
3.2.4 What Are the Risks and How They Can Be
Avoided? ...................................... 61
3.2.4.1 In the Sahel .................................... 61
3.2.4.2 In the Sudanian Zone ........................... 65
3.2.4.3 The Sudano-Guinean Subzone. . .. . . . . . . . . . . . . . . . . 65
3.2.5 Environmental Difficulties of Development.
Disasters: What Disasters? ....................... 66
3.2.5.1 Overgrazing .................................... 67
3.2.5.2 Overcropping and Deforestation .................. 68
3.2.6 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.3 Egypt: An Example of the Misapplication of High
Technology Leading to Man-Made "Desertification" 70
3.3.1 Causes of Land Degradation ..................... 70
3.3.2 Processes of Land Degradation ................... 71
3.3.2.1 Water Thble Rising .............................. 71
3.3.2.2 Absence of Nile Alluvium Resulting in Wind
Erosion........................................ 71
3.~.2.3 Loss of Nutrients ............................... 71
3.3.3 Effects of Land Degradation ..................... 72
3.3.4 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
3.4 China: A Sophisticated lhlditional Intensive
Agriculture Beginning to Be Modified by High
Technological Methods and "Desertification"
or Land Degradation ............................ 72